1. Field of the Invention
The present invention is generally in the field of electrical circuits and systems. More specifically, the present invention is in the field of power conversion and regulation in electrical circuits and systems.
2. Background Art
Power converters based on a flyback power supply topology can be used in a variety of electronic circuits and systems. For example, light-emitting diode (LED) drivers utilizing a flyback design offer an inexpensive solution providing an isolated output compliant with Underwriters Laboratories® (UL®) safety standards in fixtures that are not double insulated. In addition, such LED flyback drivers are typically capable of meeting Department of Energy (DOE) ENERGY STAR requirements, making the flyback topology an attractive design choice for relatively low power lighting applications.
Because the output of a flyback power converter is isolated from its primary circuit, many conventional approaches to providing power regulation require use of an opto-isolator to obtain feedback from the output. For example, when used as an LED driver, the LED output current is typically sensed and fed back to the primary circuit using the opto-isolator. However, addition of the opto-isolator circuitry to the flyback converter design adds cost and may reduce reliability in applications, such as LED lighting applications, where extended operating lifetimes are typically expected.
Due to the disadvantages associated with use of an opto-isolator, some flyback power converter designs use an alternative approach in which the current in the primary circuit is sensed as a proxy for the load current. Regulation of the output is then performed on the basis of the primary circuit current. This alternative approach works on the assumption that the input voltage and load do not change significantly, which has some value for a narrow range of highly predictable usage environments. However, for use over a wide input voltage range or with different loads, sensing the primary circuit current is inadequate, and a closed loop architecture including an opto-isolator is usually required.
Thus, there is a need to overcome the drawbacks and deficiencies in the conventional art by providing a flyback power converter and driver suitable for use over a wide input voltage range as well as differing loads, that does not require use of an opto-isolator or other dedicated feedback circuitry.